Rainbow

After the Deluge the hope grew into faith that no such
or similar destruction would again come to decimate mankind. The story
is told that the Lord made a covenant with Noah, and the following were
the terms of the covenant:

Then God said to Noah. . . . I establish my
covenant with you, that never again shall all flesh be cut off by the
waters of a flood, and never again shall there be a flood to destroy
the earth. (1)

As a visible sign of the obligation not to repeat the
catastrophe, a colorful rainbow appeared for the first time after the
Delugeit was a new and till then unknown atmospheric phenomenon.
In this colored refraction of sunlight in small and suspended drops of
water the rescued believed to see the divine promise not to repeat the
flood:

And God said, This is the sign of the covenant
which I make between me and you and every living creature that is with
you, for all future generations: I set my bow in the cloud, and it shall
be a sign of the covenant between me and the earth. When I bring the
clouds over the earth and the bow is seen in the clouds, I will remember
my covenant.(2)

The covenant, according to the moral conception of the
Hebrews, was a reciprocal deed. It was kept only in its promise not to
bring a paramount flood upon the Earth: the Earth and man continued to
be shaped and reshaped in further catastrophes before the close of the
age of creation that is the theme of the Book of Genesis.

References

Genesis IX.
8-11.

Genesis IX.
12-15. [According to Genesis II. 5-6 no rain
fell on the newly created earth, which was watered only by a mist
ascending from the ground and falling as dew. If this phenomenon persisted
until the Deluge this would explain the novelty of the rainbow after
the catastrophe.

Pedro Sarmiento de Gamboa,
the Spanish conquistador who traveled in the Andes in the sixteenth
century, recorded in his Historia de los Incas a tale about
Manco Capac, the first Inca, which has a curious resemblance to the
Biblical story. Emerging from a cave after the re-appearance of the
sun, Manco Capac and his brothers arrived at the mountain which
is two leagues, approximately, from the town of Cuzco, and climbing
to the top, they saw in it the rainbow, which the natives call guanacuari.
And, interpreting it as a favorable omen, Manco Capac said: Consider
this a sign that the world will not again be destroyed by water
("Tened aquello por senal que no sera el mundo mas destruido por
agua! Chapter 12). The rainbow was depicted on the altar
of the Coricancha in the temple of Viracocha in Cuzco. See R. T. Zuidema,
La Imagen del Sol y la Huaca de Susurpuquio en el Sistema Astronomico
de los Incas en el Cuzco, Journal de la Societe de Americanistes
LXIII (1974-76), p. 218. If, as Dwardu Cardona has suggested,
the reference to the rainbow in this passage is to the rings of Saturna
suggestion with which I tend to concurthe bondage
of Saturn in its rings may have been regarded as a guarantee of its
future behavior.].